Polyethylene resins have high mechanical strength, are excellent in terms of chemical resistance, corrosion resistance, etc., are inexpensive, have satisfactory moldability, and are capable of conforming to environmental issues and resource recycling. Polyethylene resins are hence in extensive use as various household materials and industrial materials. For example, the resins are used in a variety of applications including products molded or formed by injection molding, extrusion molding, blow molding, etc., such as plastic bags supplied by stores on purchase, packaging materials for foods, films for agricultural uses, tubular molded articles, e.g., pipes and hoses, and containers for shampoos, liquid detergents, and edible oils.
However, polyethylene resins are prone to be electrostatically charged since the resins have no polar groups in the molecular structure. There are hence cases where molded articles of polyethylene resins, when rubbed, exposed to flows of organic solvents, etc., or placed in low-humidity environments, suffer surface charging to attract dust or soot, resulting in product surface fouling.
Techniques in which an electroconductive carbon filler or the like is added to a polyethylene resin for the purpose of imparting electrical conductivity thereto have been proposed so far. However, there is a problem in that the addition of electroconductive fillers to polyethylene resins results in decreases in mechanical property and flowability.
Polyolefin resin compositions to which electrical conductivity has been imparted by adding an electroconductive carbon filler to the polyolefin resins and processes for the production thereof have been proposed, for example, in patent document 1 to patent document 5.
Meanwhile, since polyethylene resins have no polar groups, production of layered structures using a polyethylene resin in combination with a material of a different kind, such as a synthetic resin having polar groups, a metal, or wood, encounters a problem in that adhesion between the two is exceedingly weak or the polyethylene resin does not adhere to the adherend.
Techniques for improving the extremely low adhesiveness of polyethylene resins have been disclosed. Examples thereof include: a method in which an unsaturated carboxylic acid or the like is caused to add to a high-pressure-process low-density polyethylene resin or a polyethylene resin produced by the medium- or low-pressure process, thereby imparting adhesiveness thereto (see, for example, patent document 6); and a method in which ethylene is copolymerized with a polar-group-containing vinyl monomer using a high-pressure radical polymerization process to obtain an olefin copolymer containing polar groups (see, for example, patent document 7 and patent document 8).
Although there is a desire for a polyethylene resin material in which the charging properties and the poor adhesiveness to different kinds of materials, which are drawbacks of polyethylene resins, have been improved and which retains the excellent properties originally possessed by polyethylene resins, it has been impossible to produce such a material with any prior-art technique.
Patent document 9 proposes, as a polyolefin resin which combines electrical conductivity and adhesiveness, a polypropylene resin composition obtained by compounding a polypropylene resin having specific properties with a modified polypropylene in which polar groups derived from maleic anhydride or the like have been introduced into the molecular chain and with electroconductive carbon.
Patent document 10 proposes a semiconducting mixture which exhibits excellent performance when used in PTC elements, the semiconducting mixture being obtained by adding two carbon blacks each having a specific property range to high-density polyethylene having molecular chain terminals modified with an acid anhydride, and further proposes a PTC element.